1 files changed, 90 insertions, 24 deletions

diff --git a/src/duckdb/Result.zig b/src/duckdb/Result.zig
index 2b5b992..53ed351 100644
--- a/src/duckdb/Result.zig
+++ b/src/duckdb/Result.zig
@@ -5,49 +5,52 @@ const c = @cImport({
 
 
 pub fn Result(comptime T: type) type{
+    const column_count = switch (@typeInfo(T)) {
+        .Struct => |v| v.fields.len,
+        .Void => 0,
+        else => @compileError("Expecting struct or void in query result type"),
+    };
 
     return struct {
-        _res:   c.duckdb_result,
-        _chunk: c.duckdb_data_chunk,
+        _res:         c.duckdb_result,
+        _chunk:       c.duckdb_data_chunk,
+        _columns:     [column_count]c.duckdb_vector,
+        _validities:  [column_count]?[*]u64,
+        _data:        [column_count]?*anyopaque,
+
+        _current_row: usize,
 
         const Self = @This();
 
         pub fn init(conn : c.duckdb_connection, query: [:0]const u8) !Self {
             var self : Self = .{
-                ._res   = undefined,
-                ._chunk = null
+                ._res            = undefined,
+                ._chunk          = null,
+                ._columns        = undefined,
+                ._validities     = undefined,
+                ._data           = undefined,
+                ._current_row    = 0,
             };
             const state = c.duckdb_query(conn, query, &self._res);
             if ( state == c.DuckDBError){
                 return error.DuckDBError;
             }
-            self.fetchDataChunk();
-
-            // Get column vectors
-            switch (@typeInfo(T)) {
-                .Struct => |v| {
-                    const column_count = v.fields.len;
-                    var columns : [column_count]c.duckdb_vector = undefined;
-                    for (columns, 0..) |_, i| {
-                        columns[i] = c.duckdb_data_chunk_get_vector(self._chunk, i);
-                    }
-                    std.debug.print("{any}", .{columns});
-                },
-                .Void => {},
-                else => @compileError("Expecting struct or void in query result type"),
-            }
 
+            self.fetchDataChunk();
             return self;
         }
         pub fn deinit(self: *Self) void {
             c.duckdb_destroy_result(&self._res);
-            c.duckdb_destroy_data_chunk(&self._chunk);
+            if (self._chunk != null){
+                c.duckdb_destroy_data_chunk(&self._chunk);
+                self._chunk = null;
+            }
         }
 
         /// There's not way to know how many total elements we have, but we can
         /// know how many we have in the current chunk.
         fn getCurrentChunkSize(self: Self) usize {
-            if (self._chunk != null) {
+            if (self._chunk == null) {
                 return 0;
             }
             return c.duckdb_data_chunk_get_size(self._chunk);
@@ -63,8 +66,18 @@ pub fn Result(comptime T: type) type{
         fn fetchDataChunk(self: *Self) void{
             if (self._chunk != null){
                 c.duckdb_destroy_data_chunk(&self._chunk);
+                self._chunk = null;
+                self._current_row = 0;
             }
             self._chunk = c.duckdb_fetch_chunk(self._res);
+            for (self._columns, 0..) |_, i| {
+                const col = c.duckdb_data_chunk_get_vector(self._chunk, i);
+                self._columns[i]    = col;
+                self._validities[i] = c.duckdb_vector_get_validity(col);
+                self._data[i]       = c.duckdb_vector_get_data(col);
+            }
+            self._current_row = 0;
+
         }
 
         pub fn exausted(self: Self) bool{
@@ -73,10 +86,63 @@ pub fn Result(comptime T: type) type{
 
         /// We need some comptime magic to create the output structures from
         /// the T.
-        pub fn next(self: *Self) T{
-            const result: T = undefined;
-            _ = self;
+        pub fn next(self: *Self) !T{
+            var result: T = undefined;
+            const fields = comptime switch (@typeInfo(T)) {
+                .Void => .{},
+                else  => |f| f.Struct.fields,
+            };
+
+            if (self._current_row == self.getCurrentChunkSize()){
+                self.fetchDataChunk();
+            }
+
+            inline for (fields, 0..) |field, i| {
+                // TODO: check compatibility between the column type and
+                // the struct provided as result container
+                //
+                // const column_type = c.duckdb_column_type(&self._res, i);
+                // std.debug.print("tipo => {any}\n", .{column_type});
+                // std.debug.print("{any}\n", .{self._data});
+
+                // Check validity
+                const entry_idx     :usize = self._current_row / 64;
+                const idx_in_entry  :u6    = @intCast(@mod(self._current_row, 64));
+                const one           :u64   = 1;
+                var   is_valid      :bool  = false;
+                if (self._validities[i]) |v| {
+                    const num = v[entry_idx] & @shlExact(one, idx_in_entry);
+                    is_valid = num != 0;
+                }
+
+                // Store the column in current row
+                if (is_valid){
+                    // Unwrap the Optional
+                    const t = switch (@typeInfo(field.type)){
+                        .Optional => |t| t.child,
+                        else => field.type
+                    };
+                    const col : [*]t = @alignCast(@ptrCast(self._data[i]));
+                    @field(result, field.name) = col[self._current_row];
+                } else {
+                    // Got a NULL from the DB
+                    if (@typeInfo(field.type) != .Optional){
+                        // Cannot return it because it's not optional
+                        return error.NullInNotOptional;
+                    }
+                    @field(result, field.name) = null;
+                }
+            }
+            self._current_row += 1;
             return result;
         }
+
+
+
+        // pub fn giveMeAll(){
+        //     // TODO: know the chunk length and use it
+        //     while (self._current_row < self._chunk_size) : (self._current_row += 1){
+        //     }
+        // }
     };
 }